ECG Circuit problem

Discussion in 'General Electronics Chat' started by Johnny1010, Jan 18, 2016.

  1. Johnny1010

    Thread Starter Member

    Jul 13, 2014
    83
    2
    Hello everyone, I am using the attached circuit schematic to get ECG signal, Instead of getting ECG signal, the output looks like as in the attached image, the output signal is taken at the node between R2(100k) and R5(100k) after the low pass filter. The PQRS peaks are not comprehendable. The instructable I am following gets a clean ECG. Is there a possibility that the oscilloscope power noise is being coupled. Any Help would be appreciated. here is the link to the instructable I am following:
    http://www.instructables.com/id/Electrocardiograph-Heart-Rate-Monitor/
     
  2. AnalogKid

    Distinguished Member

    Aug 1, 2013
    4,533
    1,251
    The circuit has a couple of issues, but first - What country are you in, and what is your AC mains frequency?

    ak
     
  3. Johnny1010

    Thread Starter Member

    Jul 13, 2014
    83
    2
  4. AnalogKid

    Distinguished Member

    Aug 1, 2013
    4,533
    1,251
    So is the waveform you posted. Where was the ground clip connected?

    ak
     
    Last edited: Jan 18, 2016
  5. Johnny1010

    Thread Starter Member

    Jul 13, 2014
    83
    2
    @AnalogKid The ground clip of the oscilloscope is connected to the common ground of the supplies (i.e. of the 9V batteries) in the schematic.

    I just connected the output of the circuit to the arduino uno instead of the oscilloscope trying to keep everything battery powered and the results appear to be something closer to an ECG.
    ecg1.png
     
    Last edited: Jan 18, 2016
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